Thursday, September 17, 2015

To Ballast or Not To Ballast, That is the Ignition!

Way back in June this year, I had a 'slight' issue when the car spluttered to a halt and refused to start again. Lifting the bonnet to see what had happened, I was confronted with the horror scenario of smoking, melting wires. Panic set in and I quickly pulled the battery connectors off as I had visions of the thing setting on fire!

Since then, the car has been off the road as I've been busy building the new engine and also prepping the car ready to receive the new engine, but now the time has come to finally deal with the problem. As with any problem like this, I've been reading around the subject and watching videos on youtube in an effort to understand what caused the issue and more importantly, how to fix it.

I must admit at this point that before I started, I knew absolutely nothing about how a car ignition system worked, as far as I was concerned, it might as well have been magic. But after a lot of reading and a few videos, the best of which was a set of four by MOSS, I started to get a grasp of the way the system worked and also the difference between a ballasted and a non-ballasted system.

If you're really interested in the differences, I'd recommend watching the videos before attempting to wade through my 'cobbled together with my limited knowledge' attempt here. For those who prefer the 'cobbled together, limited knowledge' version though, I'll try my best to explain.

Non-Ballasted Ignition System
In the beginning there was the humble ignition system and it was good. It had a 3 ohm coil and ran at the standard 12.6 volts supplied from the battery and all was well. You turned the key and the ignition system did it's thing and the car started. However, there comes a point in every year when a curse descends upon the land and all becomes frozen and dark. This phenomenon, that some call winter has a number of less than helpful effects on a car that has been sat out in the chill all night.

The oil becomes thicker, belts stiffen, metal shrinks and everything gets tighter and to make matters worse, the battery is attacked by the cold and some of the volts fall out!! All this means that a depleted battery is trying its very best to turn a cold tight engine, while at the same time also trying to create a spark. The result is that depressing noise as the battery slowly dies and you're left sat there thinking: "I hate this car".

So to fix this problem, the automotive boffins of the day got together, stroked their beards and scratched their heads and came up with a plan. A very clever plan that cleverly solved the cold start problem and they cleverly called it; The Ballasted Ignition System.

This somewhat leaves the first system without a proper name as it was simply known as 'an ignition system' as there was nothing to differentiate against it. But from that day forth it became known as 'The Not-So-Good In Winter Ignition System', although most literature both then and now will refer to it a Non-Ballasted Ignition System.

To understand why a Non-Ballasted Ignition System was not-so-good in winter, a little mathematics will now be deployed, but don't worry, it's mostly harmless and not the very scary type!

To understand the maths, I will use two little triangles shown below:

V = Volts
R = Resistance in ohms
A = Amps
W = Power in watts

The way I use them is to cover the letter of the part I want to work out with my finger and the formula I need is left behind. For example, using the first triangle, I want to work out the amps for a given system so I cover the A and I’m left with V divided by R.

Or, using the second triange, if I want to know what W is, I end up with A multiplied by V. It’s all very simple stuff you probably learnt at school and forgot, that’s certainly the case for myself anyway.

Using these triangles is dead simple to calculate what we need to know.

Non-Ballasted Scenario 1 - Ideal Battery Voltage
In a Non-Ballasted system with a normal battery voltage of 12.6 volts and a 3 ohm coil, we need to work out how many amps are being drawn:
V = 12.6
R = 3

So to work out the amps (A), it’s Voltage divided by Resistance
V/R = A
12.6 / 3 = 4.2 Amps

Now we take that 4.2 Amps and feed it into the second triangle to determine how much power (in Watts) the coil is using to make a spark.

So to work out the power in Watts (W), it’s Amps multiplied by Voltage

Which is: A x V = W
4.2 x 12.6 = 52.92 Watts

52.92 Watts is about the same as an older style light bulb and that’s what’s creating the spark.

Non-Ballasted Scenario 2 - Low Battery Voltage
Now if that same Non-Ballasted system was suffering from a cold and frosty battery that was only able to muster up a meagre 10 volts, then the situation would look like this:
V = 10
R = 3

So to work out the amps (A), it’s Voltage divided by Resistance
V/R = A
10 / 3 = 3.33 Amps

Just as before, we take that 3.33 Amps and feed it into the second triangle to determine how much power (in Watts) the coil is using to make a spark.

So to work out the power in Watts (W), it’s Amps multiplied by Voltage

Which is: A x V = W
3.333 x 10 = 33.33 Watts

As you can see in the second scenario there’s only a feeble 33 Watts of power to make a spark compared to the ideal scenario of 53 Watts. To make matters worse, the longer you crank that starter, the lower the voltage will get until the battery is dead!!!

Ballasted Ignition System
So along comes a new era in cold morning car starting with the ballasted system. The system differs in two main ways, firstly the coil is designed to run at a lower voltage and has half the resistance of its non-ballasted counterpart with just 1.5 Ohms.

Ballasted Scenario 1 - On Start Up
So let’s run the numbers again
V = 12.6
R = 1.5

So to work out the amps (A), it’s Voltage divided by Resistance
V/R = A
12.6 / 1.5 = 8.33 Amps

Now we take that 8.33 Amps and feed it into the second triangle to determine how much power (in Watts) the coil is using to make a spark.

So to work out the power in Watts (W), it’s Amps multiplied by Voltage

Which is: A x V = W
8.33 x 12.6 = 104.95 Watts

Yup, that’s a massive 104.95 Watts available to make a mega spark!

Of course if you run the coil at that power level for too long something is going to melt! Remember how hot a 100 Watt bulb used to get?? So to solve this problem the 12.6 Volt feed is switched on and off by the starter motor solenoid, meaning that the coil only gets the mega boosting 12.6 volts for the few seconds that you are cranking the starter.

For the rest of the time the coil is fed via a ‘special’ resistive wire that reduces the voltage from the 12.6 battery output to somewhere in the region of about 9 Volts. This resistive wire is the actual the ballast and what gives the system it’s name.

To work out the amps (A), it’s Voltage divided by Resistance
V/R = A
9 / 1.5 = 6 Amps

Now let’s take that 6 Amps and feed it into the second triangle to determine how much power (in Watts) the coil is using to make a spark.

A x V = W
6 x 9 = 54 Watts

This is almost identical to the 52 Watts of power the Non-Ballasted, 12.6 Volt, 3 Ohm coil created. So even if the battery voltage has dropped to somewhere in the region of 9 volts, the Ballasted system will still start the car and continue to run without melting. It’s the perfect solution.

So how do you know which system you have, well the simplest way is to look for a pink/white resistive cable going to the positive side of the coil. If that's present, it's ballasted.

Fixing My Wiring
So with all this super duper knowledge under my belt I set to work trying to find a replacement 1.5 Ohm length of pink/white resistive wire to replace my melted one. After a lengthy internet search proved fruitless, I decided to order normal ignition wire and a ballast resistor instead.

The first job I had was to trace the pink/white ballast cable back to its origin and cut it out. Once that was done, I crimped in a new length of white ignition cable which followed the existing loom and terminated at one end of the ballast resistor.

Out with the old...

In with the new

Next thing to sort was finding somewhere to mount the ballast resistor. Luckily it came fitted to a mounting plate and after drilling the hole a little larger; I attached it just above the coil. The last thing was to attach the wire that came out of the ballast resistor to the positive side of the coil.

And that's it really, it's all done and that represents the last obstacle to starting the engine, so guess what's next up on the agenda??? Engine Start!!!!!!!!!!!!!!!!!!!

1 comment:

Hi, very nice write up! I'm having issues with my ballast ignition system so I'm thinking of replacing the resistor wire as you did... Can you remember where the other end of the wire is before I start unwrapping the whole loom?Thanks.